This invention relates to a filter for the separation of impurities from exhaust gases, and in particular, from exhaust gases of an internal combustion engine, having a filter body consisting of a plurality of compression-moulded and sintered filter plates with high temperature stability made from powdered metal, metal filings, metal fibers or a mixture thereof, which are disposed on top of one another or behind one another respectively, are separated by spacers and form a plurality of flow ducts between them, with the flow ducts being open on one side and closed on the other side so as to form inlet and outlet ducts respectively, and with the walls of the filter plate lying between the inlet and outlet ducts representing filter surfaces.
In the exhaust gases from a diesel engine in particular, there is a plurality of soot particles which can cause problems if, apart from an elimination of the soot from the exhaust gases, one would also wish simultaneously to remove further impurities or harmful exhaust gas constituents by catalytic action.
Thus, for example, a good catalytic function of the conversion of carbon monoxide and hydrocarbons by catalytic materials is not possible when a filter is charged with soot.
Therefore it is known firstly to clean the soot particles from the exhaust gases by a filter, and then to direct the exhaust gases cleaned in this way over a catalyst connected behind said filter. However a disadvantage of this arrangement is that it is very expensive and therefore very uneconomical.
In the prior West German applications P 39 01 609.9 and P 39 37 809.8 from the same applicant, filters have already been proposed, especially for the removal of soot particles, which consist of a plurality of compression-moulded and sintered filter plates with high temperature stability of the type mentioned at the beginning.
The object of the present invention is to create a filter of this type, and to improve it so that both a removal of soot particles, and also a catalytic function for the elimination or conversion of further impurities and harmful constituents in the exhaust gases, is possible in a single filter unit and as far as possible without reciprocal disadvantageous influence.